Automated railroad crossing gate management system

ABSTRACT

A gate system for an intersection of a railroad track and roadway has detectors to monitor the intersection and crossing relays to monitor the railroad track. A controller connected to the detectors and the crossing relays operates the gates to prevent the gates from trapping a vehicle on the tracks.

RELATED APPLICATION

[0001] This patent application claims the benefit of the filing date of provisional patent application Ser. No. 60/287,989 filed on May 1, 2001.

FIELD OF THE INVENTION

[0002] The present invention relates to railroad crossing gate systems and, more particularly to, an improved gate management system that provides management and control of four traffic gates located at a railroad intersection for preventing vehicles from entering the path of an approaching locomotive.

BACKGROUND OF THE INVENTION

[0003] Grade crossings, where motor vehicle traffic crosses railroad tracks, have been a notorious site for collisions between the motor vehicles and trains. Two types of gate systems have been used to block road traffic from the approach of the train. A two quadrant gate system utilizes entrance gates to prevent approaching motorists from entering the crossing. Two quadrant gate systems, however, have no exit gates to block motorists that are exiting the crossing area. A problem arises when motorists drive around the lowering or lowered entrance gates into the exit of the oncoming lane. This problem is exacerbated with high-speed rail traffic, because the motorists may not see the approaching train and are more likely to violate the necessary clearance space as the train reaches the crossing.

[0004] To limit motorists' violations of two quadrant gate warning systems, a four quadrant gate may be utilized to prevent motorists from driving around the entrance gates and into the grade crossing. Four quadrant gate systems have exit gates that create a full barrier across the roadway to block motorists from entering the crossing area after the gates are fully horizontal. If, however, a motorist has entered the crossing as the entrance gate is closing, the motorist may be trapped in the crossing by the exit gate.

[0005] It would, therefore, be desirable to have an improved railroad crossing gate system that does not allow a motorist to drive around an entrance gate of the crossing. It would also be desirable to have an improved railroad crossing system that does not trap motorists within the railroad crossing.

SUMMARY OF THE INVENTION

[0006] A gate system for an intersection of a railroad track and roadway, the roadway having two lanes of opposing vehicular traffic, the opposing vehicular traffic generally having a first direction and a second direction has a first entrance gate located proximate a first lane of the roadway. The first entrance gate is operable between an open and closed position to control vehicular travel across the railroad track from the first direction. A first exit gate is located proximate the first lane of the roadway. The first exit gate is operable between an open and closed position to control vehicular travel across the railroad track from the second direction. A second entrance gate is located proximate a second lane of the roadway, the second entrance gate operable between an open and closed position to control vehicular travel across the railroad track from the second direction. A second exit gate is located proximate the second lane of the roadway. The second exit gate is operable to control vehicular travel across the railroad track from the first direction. One or more detectors monitor the intersection to detect a vehicle proximate to the intersection. One or more crossing relays monitor the railroad track to detect a train proximate the intersection. A controller connected to the one or more detectors and the one or more crossing relays operates the gates to prevent the gates from trapping a vehicle on the tracks.

[0007] A method for controlling gates at an intersection of a railroad track and roadway has the steps of detecting a train proximate the intersection and monitoring the status of one or more detectors proximate the intersection to determine presence of a vehicle proximate the intersection. One or more exit gates are operated if a vehicle is detected proximate the intersection.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a more complete understanding of the present invention, including its features and advantages, reference is now made to the detailed description of the invention, taken in conjunction with the accompanying drawings of which:

[0009]FIG. 1 is a site plan of a conventional grade crossing showing one embodiment of the gate management system of the present invention; and

[0010]FIG. 2 is a front view of a control panel of one embodiment of the present invention.

DETAILED DESCRIPTION

[0011] While the making and using of various embodiments of the present invention is discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention, and do not delimit the scope of the invention.

[0012] Referring now to the drawings and more particularly to FIG. 1, a railroad grade crossing is generally designated 10 with the railroad tracks 12 and a road 14 oriented generally transverse to tracks 12 with vehicles 16 thereon. A train 18 on tracks 12 may approach the intersection of the railroad tracks 12 and the road 14 from either direction.

[0013] As shown in FIG. 1, an Exit Gate Management System (EGMS) 20 controls exit gate timing as a part of a larger Four-Quadrant Gate Control System, designated generally as 30. The EGMS 20 may include vital inductive loop vehicle detectors (50, 50′, 52, 52′, 54, 54′) to detect automotive traffic within the area between the entrance gates 60, 62 and exit gates 60′, 62′ (Minimum Track Clearance Distance—MTCD). If a vehicle 16 is detected, the exit gates 60′, 62′ may not be lowered until the vehicle clears the MTCD. The EGMS 20 is designed using railroad standards and vital principles. As a backup mode, automatic changeover may be utilized in the event of inductive loop vehicle detector (50, 50′, 52, 52′, 54, 54′) failure.

[0014] Each exit gate 60′, 62′ may be held in or forced to the vertical position based on detection of vehicle traffic within the crossing area (MTCD). If no vehicles 16 are present within the MTCD when the warning system is activated, the exit gates 60′, 62′ may descend simultaneously with the entrance gates 60, 62. Any vehicle 16 present within the MTCD when the warning system is activated may cause the exit gate 60′, 62′ toward which the vehicle 16 is moving to remain vertical or, if started down, to return to vertical. After the vehicle 16 clears the MTCD, the exit gates 60′, 62′ may be driven down. The exit gates 60′, 62′ are designed as “fail up”, so that the removal of power to the exit gate 60′, 62′ or problems with the crossing system may cause the exit gates 60′, 62′ to rise to the vertical position.

[0015] In the event of a detector (50, 50′, 52, 52′, 54, 54′) failure, the detector-based exit gate 60′, 62′ operation may be disabled. To provide continued four-quadrant crossing warning, the EGMS may revert to timed exit gate 60′, 62′ operation. Upon removal of the XR signal and the beginning of entrance gate 60, 62 decent, the EGMS 20 may delay the exit gates 60′, 62′ by a pre-programmed interval. After the delay has been timed, the exit gates 60′, 62′ may be lowered.

[0016] A detector (50, 50′, 52, 52′, 54, 54′) may be a “Vital Inductive Loop Detector” (VLD). Recent advances in microprocessor circuitry and vehicle detection research have made the inductive loop one of the most reliable vehicle detection technologies available today. With the addition of railroad-standard vital techniques, the Vital Inductive Loop Detector provides outstanding reliability along with vital self-checks and failure detection.

[0017] Loop placement may correspond to the number of tracks 12, 12′ and the number of vehicular traffic lanes at the crossing. Loops (50, 50′, 52, 52′, 54, 54′) may be installed between the entrance gate 60, 62 and first track, between the last track and the exit gate 60′, 62′, and between each track 12, 12′. A single loop may be used to separate sets of loops may be used for each direction of travel. The loop configuration may be determined by the physical configuration of the crossing and an analysis of the crossing location.

[0018] The EGMS 20 may operate in conjunction with a Four-Quadrant Gate Control System. The EGMS 20 may include vital inductive loop vehicle detectors (50, 50′, 52, 52′, 54, 54′) to detect automotive traffic within the Minimum Track Clearance Distance (MTCD), which is the area between the entrance and exit gates, and the vital processing logic required indicate the presence of automotive traffic and the direction of travel of that traffic.

[0019] Four-Quadrant gate systems may incorporate exit gates 60′, 62′ so that there is a full barrier across the roadway 14 to prevent vehicles 16 from entering the crossing area after the gates (60, 60′, 62, 62′) are fully horizontal. To prevent entrapment of vehicles 16 within the crossing area (MTCD), the exit gates 60′, 62′ may be controlled in a manner that provides the opportunity for vehicular traffic to clear the MTCD prior to closure of the exit gates 60′, 62′. Two Exit Gate Operating Modes (EGOMs) exist to prevent vehicle entrapment. The simplest mode is by using “Timed EGOM”, in which the exit gates 60′, 62′ may be lowered after a pre-determined delay following the release of the entrance gates 60, 62. The second, more complex mode of exit gate control may incorporate vehicle detection to prevent exit gate decent while vehicles are present within the crossing area. This method, called “Dynamic EGOM”, may provide a higher level of safety than the delay mode to reduce the likelihood of trapping a vehicle within the MTCD, which may be stopped by a downstream traffic delay such as a turning vehicle 16 beyond the crossing or delay by a highway traffic signal. By monitoring vehicle occupancy, the exit gates 60′, 62′ for each direction of traffic may be independently controlled to assure no vehicle is between the entrance gate 60, 62 and exit gate 60′, 62′ prior to exit gate descent. The EGMS 20 may use vehicle detection for primary exit gate control. As a backup mode, Timed EGOM may be utilized in the event of inductive loop failure. Both modes are described in detail below.

[0020] The VLD may include a vital “self-check” operation. A secondary loop wire may be installed along with the primary inductive loop. The VLD periodically manipulates the secondary loop and monitors the primary loop for the expected change of inductance. Using this self-check mechanism, the VLD may positively verify that the inductive loop, wiring, and detection circuitry are operating properly. Any problems detected by the self-check operation may cause both the health and detect outputs to drop.

[0021] Loop placement may correspond to the number of tracks and the number of vehicular traffic lanes at the crossing. Loops may be installed between the entrance gate and first track, between the last track and the exit gate, and between each track. A single loop may be used to cover multiple lanes, or one or more loops may be used for a single lane. The final loop configuration may be determined using geometric factors at the crossing and during an analysis of each crossing location.

[0022] If multiple loops are located in close proximity to each other, there may be a chance for cross-talk and interference between the loops if both loops are actively “scanning” simultaneously. The VLD may be designed to operate in a “sequential scan” mode, such that only one loop is active at a time. Using sequential scan mode, loops may be placed as needed for proper coverage and vehicle detection, without concern for loop cross-talk and interference.

[0023] The VLD may include a communications link to the Logic Processing System to provide secondary loop information to the system. The information provided via the communications link may include VLD control settings, loop status, vital self-check status, and sequential scan status. This information may be provided to the user via the Diagnostic Display Panel and to the event log, as described later in this document.

[0024] Upon the approach of the train, the Grade Crossing Warning System may drop the Crossing Relay (XR) signal, which initiates the operation of the entrance gates. These gates drop following the illumination of the flashing lights (typically for 3-5 seconds, as determined by the XLC or equivalent logic) and may remain in the horizontal position until the re-energizing of the XR signal. The entrance gates may be designed as “fail down”, so that the removal of power to the gate or problems with the crossing system will cause the gates to drop to the horizontal position.

[0025] The EGMS may provide a vital output, “Entrance Gate Hold”, which is energized when the EGMS determines that it is safe to raise the entrance gates. This output may be tied to the crossing system's XLC or equivalent equipment to lower the entrance gates when the output drops. Using the Entrance Gate Hold feature allows the EGMS to hold the entrance gates down and prevents situations in which an exit gate may be down when the exit gate is up (e.g. exit gate mechanism is held down by external obstruction).

[0026] The EGMS may initiate exit gate operation upon the removal of the XR signal and the loss of entrance gate vertical status. After the entrance gates begin to descend, the EGMS times a user-programmable “Dynamic Exit Gate Clearance Time” (DEGCT). Upon completion of the DEGCT, the EGMS attempts to lower the exit gates. Each exit gate may be held or forced in/to the vertical position based on detection of vehicle traffic within the crossing area (MTCD). If no vehicles are present within the MTCD when the warning system is activated, the exit gates may descend simultaneously with the entrance gates (if the DEGCT is set to zero), or after the DEGCT (if non-zero). Any vehicle present within the MTCD when the warning system is activated will cause the exit gate toward which the vehicle is moving to remain vertical or, if started down, to return to vertical. After the vehicle(s) clear(s) the MTCD, the exit gates may be driven down.

[0027] At the time the entrance gates become fully horizontal, the loop detector between the entrance gate and first rail may be ignored by the EGMS thereby preventing a vehicle that pulls up to the entrance gate from holding the exit gate up. This may be a programmable option, and may be used in cases where it is possible for vehicles to pull forward far enough under a fully-horizontal entrance gate to be sensed by the adjacent detector loop.

[0028] After all gates reach their full horizontal positions, the detection system may be inhibited and the gates remain horizontal (based on user-selectable option). Also, after one or more of the Crossing System's Island Circuits (ISLAND) drop, the detection system may be inhibited and all exit gates may be dropped and held in the horizontal position. This may prevent erroneous “detection” of the train, because the loop detectors may sense the train as it passes.

[0029] The EGMS monitors entrance gate positions. If all entrance gates do not reach the full horizontal position within a pre-programmed maximum time, the exit gates may be raised. This reduces the possibility of vehicle entrapment in cases of entrance gate malfunction or breakage. The exit gates may be designed as “fail up”, so that the removal of power to the gate or problems with the crossing system will cause the exit gates to rise to the vertical position.

[0030] If a detector fails, or if the user desires simple timed EGOM, the dynamic exit gate operation is disabled. To provide continued four-quadrant crossing warning, the EGMS may automatically revert to timed exit gate operation if a detector failure occurs. Upon removal of the XR signal and the beginning of entrance gate decent, the EGMS may delay the exit gates by a pre-programmed “Timed Exit Gate Clearance Time” (TEGCT) interval. After that delay has been timed, the exit gates are lowered. Detector inputs, even if installed, may be ignored in Timed EGOM.

[0031] The Logic Processing System (LPS) may monitor all detectors, the XR signal, the ISLAND signals, and all “Gate Horizontal” and “Gate Vertical” signals. The LPS determines if vehicles are in the crossing area, and which area of the crossing the vehicle is occupying. Based on that determination, it may raise the exit gate(s) corresponding to detected vehicle(s). After all vehicular traffic has cleared the crossing area in each direction, the LPS may provide an exit gate control output to lower the corresponding exit gate(s). After all automotive traffic has cleared and all gates are horizontal, or when one or more of the Island circuits drop, the LPS may inhibit the detection of vehicles and holds all exit gates horizontal. If desired, the detection system may continue to operate with all gates horizontal, thus being disabled only when one or more of the Island circuits drop.

[0032] The LPS may provide two vital 12 vdc “Exit Gate” outputs, which may control the operation of the exit gates for each direction of vehicular traffic flow. Each of these outputs may be driven to 12 vdc to force the corresponding gate(s) into the horizontal position. Removal of the “Exit Gate” outputs allows the corresponding gate(s) to rise to the vertical position.

[0033] The LPS may provide one vital 12 vdc “Entrance Gate Hold” output, which may be used to force the entrance gates to the horizontal position regardless of the XR state. This output may be dropped in cases where the EGMS determines that it is not safe to raise the entrance gates, such as, for example, when an exit gates fails in the horizontal position by malfunction or obstruction.

[0034] The LPS may include a display to allow easy setup, testing, maintenance, and troubleshooting of the system. Such information as necessary to perform these functions may be displayed in a concise, clear, and user-friendly format.

[0035] The EGMS may provide three vital outputs to indicate the current health and state of the system. These outputs may be used individually or in combination as a means of monitoring and/or positive train control. The LPS may provide a vital 12 vdc “EGMS Health” output to the Positive Train Control (PTC) System, which may be driven to 12 vdc at all times that the system is in proper operational order and the exit gates are functioning as expected. Any problems within the EGMS that result in inoperability of the exit gates will cause the EGMS Health output to drop immediately and remain dropped until the problem is corrected and a user-entered Failure Clear command is entered. This output allows the Crossing System and PTC to determine the overall state of the crossing equipment as the train approaches, and allows alteration of the train speed as necessary. Note that the EGMS Health output may remain active even if there is a VLD failure, if the EGMS is programmed to revert to Timed EGOM on detector failure.

[0036] The LPS may provide a vital 12 vdc “VLD Health” output to the PTC System, which may be driven to 12 vdc at all times that all VLDs are functional. This output is used to determine the health of the detectors independent of the EGMS health. There are cases in which the Detector Health may drop, i.e. a failed loop wire in the road or cut cable, but the EGMS Health may remain active (and the EGMS is in Timed EGOM.). This output allow partial PTC degradation in the case of detector failure when the EGMS is operating in Timed EGOM, and allows the crossing monitoring system to register a call for system maintenance in case of detector failures.

[0037] The LPS may provide a vital 12 vdc “Detect” output to the PTC System, which may be driven to 12 vdc if no vehicles are detected anywhere within the crossing detection area. This output may be dropped if one or more vehicles are detected in the crossing area and the XR input is deenergized. This output may be driven to 12 vdc if the ISLAND circuit drops, to prevent false detection generated by the passage of the train itself. It may also be driven to 12 vdc when XR is energized, so that normal vehicle detections are ignored if no train is approaching. The “Detect” output may be used by the PTC System to indicate vehicular traffic that may be within the MTCD.

[0038] The LPS may provide a serial data communications link to the Vital Loop Detector cards for the transfer of additional loop status and data. This data link allows for “multi-drop master-slave” communications, so that multiple detector cards may be monitored by the LPS via a single link. The communications protocol may be designed for vital operation, such that a failure of the communications link or a detector card results in a known failure condition.

[0039] Referring now to FIG. 2, all equipment necessary for the EGMS may be designed for mounting in a single 19″ equipment rack. The equipment may include the Vital Loop Detector electronics, the Logic Processing System, the Diagnostics Display Panel, Isolated 12 vdc Power Supplies, the Inductive Loop Wiring Termination Panel, and the EGMS Termination Panels for vital detector signals, gate control, gate position, and Crossing Warning System interface signals.

[0040] The EGMS rack may be sized to allow for 16 detector inputs. The number of detectors required for a given EGMS installation may be determined by evaluating many factors such as the number of lanes of travel each direction, the number of tracks, the distances between gates and tracks, and the angle of the crossing, for example. The EGMS electronics chassis (which may hold all VLD and LPS electronics, along with the isolated power supplies), the termination panels, and all necessary wire management devices to ensure a neat and orderly installation may be installed within the rack. Approximately 42 vertical inches of rack space is required. The EGMS electronics chassis is approximately 9 inches deep, and an additional three inches is required for wiring, thus totaling a depth requirement of about 12 inches. The chassis mounting brackets may be located at any point along the side of the chassis, thus allowing installation in a center-rail rack or a front-rail rack.

[0041] The Inductive Loop Wiring Termination Panel may be located at the lowest location in the rack, so that the loop lead-in cabling may be terminated near the entrance location in the equipment house. The EGMS electronics chassis may be located above this panel. The EGMS Termination Panel may be located at the top, to allow ease of in-house wiring and testing.

[0042] The Inductive Loop Termination Panel (ILTP) may be designed for ease of wiring the loop lead-in cables to the EGMS. It allows the termination of up to sixteen vital loop detectors—this may include one Detection loop and one Self-Check loop per detector. The ILTP may utilize standard AAR terminals for all field wiring. Wiring connections from the ILTP to the EGMS chassis may be performed from the back of the ILTP, so that only the field wiring is exposed on the front of the panel. This panel may attach to a standard 19-inch rack and is approximately 7 inches high. All terminals may be clearly silkscreened on the panel to indicate function.

[0043] The EGMS Termination Panel (ETP) may be designed for ease of wiring, testing, tracing, and monitoring of signals between the EGMS and the remainder of the railroad crossing equipment. It may provides test points for detector vital Detect and vital Health signals, along with XR, island, gate position, EGMS gate control, and EGMS PTC signals. The ETP may incorporate WAGO cage-clamp terminals mounted on two rows of DIN rails. This panel may attach to a standard 19-inch rack and is approximately 8.25 inches high. All terminals are clearly silkscreened on the panel to indicate function. Wire management guides such as cable ties and cable feed-throughs may be used to produce a clean and orderly wiring layout.

[0044] The EGMS Logic Chassis may be a 19-inch rack-mount PC Board chassis that holds all the EGMS electronics and power supplies. The EGMS processing may be performed by the RCL standard CPU386EX circuit board. It may contain an Intel 80386EX embedded processor operating at 33 MHz, 2 MB FLASH program memory, 128 KB supercap-backed RAM (used for normal processing and short-term event log information) and 64 KB non-volatile EEPROM (used to maintain database parameters), for example. It may also contain a real-time (time-of-day) clock with supercap backup, a power monitor circuit, a watchdog timer, a mode switch, a diagnostic RS-232 serial port, and interfaces for the front panel display and the backpanel.

[0045] The CPU and chassis may be designed to allow the installation of two CPU boards. One may act as the “Primary” CPU, and the second may act as a “Secondary/Monitor”. The primary CPU may perform EGMS functions and user interface operation. The secondary CPU monitors the primary CPU for proper operation, and can gain control of the chassis if a primary CPU failure is detected.

[0046] The EGMS database parameters may be stored within each CPU's non-volatile EEPROM, and in the Memory card described below. On system startup, each CPU verifies its own database for validity, then compares its database to the other CPU and the Memory card. If any one card contains different or invalid data, the data from the two valid and compatible cards may be copied to the different or invalid card's memory. In this manner, the failure or replacement of any single card may not result in the need to re-enter system data. If the three card's memories do not match or there are not at least two cards with matching, valid data, the system may enter a standby mode until the user programs the system properly.

[0047] The EGMS Memory card may provide a data repository separate from the CPU cards. It allows database parameters to be stored in multiple locations for data verification and copy, as described above. It also contains the bulk non-volatile memory used for event logging. The memory card may be configured according to system needs. For the EGMS, the memory card may contain 256 KB supercap-backed RAM for short-term event/system history data storage, and 4 MB FLASH EEPROM for long-term non-volatile event logging storage, for example.

[0048] The EGMS Communications card may provide the ability to communicate with various devices via serial communications ports. The card may contain an RS-485 port for communications to the detector cards, as described in the VLD section of this document. It may also contain general-purpose serial ports, which may be used for system communications, dial-out error/event logging, printer connection, local laptop connection, and/or radio/fiber/twisted-pair modem connection. Each port may be configured for RS-232, RS-422, or RS-485 hardware connections, for example. Software may be configured for a number of standard and/or proprietary protocols.

[0049] The Vital Input/Output card may be configured for 32 vital input circuits, or for 24 vital inputs and 8 vital outputs, for example. It may contain multi-color LED's on its front panel to indicate the status of each input and/or output. The EGMS may also utilize one Vital I/O configured for 32 inputs, and one Vital I/O configured for 24 inputs and 8 outputs. The 32 input Vital I/O card may be used to monitor the 16 detector channels (16 “Detect” inputs and 16 “Health” inputs). The other Vital I/O card may monitor the gate positions, XR, and islands, and provides the vital outputs to the remainder of the railroad crossing equipment. One Vital Loop Detector card is manufactured by Reno A&E. The VLD cards are described in more detail below.

[0050] The EGMS maintenance diagnostic display panel (MDDP) may allow direct data entry and system monitoring. It may include a backlit LCD with an integral touch-screen. In graphics mode, the LCD is capable of 320 by 240 resolution (“quarter-VGA”), and in text mode it can display up to 30 lines of 50 characters each. The current state of the EGMS, including gate positions, detectors, XR, islands, and output may be illustrated by a graphical representation. A “playback” mode may also be available (which re-creates a crossing operation by displaying the event log in a progressive fashion).

[0051] All information, including database parameters, current input states and status, current operating mode and status, output modes, and event log, may be displayed textually. All database entries may be edited and stored from the diagnostic display panel, as well. The viewing and altering of information and database parameters may be restricted by multi-level password protection. Multiple passwords may be assigned for read-only and read/write access. Any user log-in, log-out, and database changes may be logged to the event log. The MDDP may plug directly into the CPU boards from the front of the rack. It may contain a switch to allow the viewing of either the primary or secondary CPU data. This allows the user to access the active CPU for current operating information, as well as the inactive CPU for the monitoring of the backup functionality. The EGMS may function with or without the MDDP installed.

[0052] The EGMS power supply card may provide electrical isolation from the battery source. It generates isolated +5 vdc and −5 vdc for the EGMS logic, and isolated +12 vdc for the EGMS vital I/O processing and detectors. The power supply may be fully fused and its circuitry may be protected against overloads and short circuits. All EGMS logic and equipment may be powered through this power supply card, so that full isolation is established.

[0053] The loop detector module may respond to pre-set changes in the inductance of the sensor loop/lean-in combination(s) connected to its loop input terminals. It may develop a detection output when there is a sufficiently large decrease in the magnitude of the connected inductance. The loop detector module may incorporate such inductive loop tuning and sensitivity adjustments as necessary to provide accurate and reliable detection of vehicular traffic while minimizing false detection. The loop detector module may operate from an external nominal 12 vdc power source. The voltage range may be 9 vdc minimum to 18 vdc maximum. The maximum ripple may be 500 millivolts peak to peak.

[0054] The loop detector power supply may be electrically isolated from the 12 vdc power source. This may be achieved using either internal power isolation or the use of an external 12 vdc isolated supply. The loop detector module may meet or exceed the environmental requirements as specified in section 6.5.2.5 (ENVIRONMENTAL REQUIREMENTS) of the NEMA TS2-1992 document. These requirements include temperature, humidity, voltage transients, vibration, and shock.

[0055] The loop detector module may be configured and dimensioned as a four-channel detector card, as specified in section 6.5.2.2 (CONFIGURATIONS AND DIMENSIONS) of the NEMA TS2-1992 document. Each card may contain multiple fully functional loop detectors. Each detector module may provide separate and independent vital “Health” outputs. These outputs may generate an isolated, vital 12 vdc voltage at such time as the detector and corresponding sensor loop/lead-in combination(s) are functioning properly. Each detector module may provide separate and independent vital “Detect” outputs, one per detector channel on the card. These outputs may generate an isolated, vital 12 vdc voltage at such time as the detector does not detect the presence of vehicular traffic within the corresponding sensor loop(s) detection zone(s).

[0056] The detector may incorporate a vital “self-check” operation to verify proper operation of the sensor loop/lead-in combination(s). The detector “self-check” may utilize a secondary loop, installed along with the primary sensor loop. The detector may periodically activate the secondary loop in such a way that an inductance change is generated on the primary sensor loop. The detector may monitor the corresponding change in induction on the primary sensor loop.

[0057] Based on the primary loop inductance change, the detector may determine the proper operation of the primary sensor loop(s), lead-in(s), and detection circuitry. Failure of the self-check may cause the detector to deactivate its “Health” and “Detect” outputs, and may remain in that state until the problem has been corrected and the detector has been reset. The self-check operation may commence at a user-programmable time period, subject to normal detector operation. The detection of vehicles in normal operation may reset the self-check period, so that the self-check only occurs when no vehicle detections have been processed during the user-programmable time period. The self-check operation does not typically affect the “Detect” output. That is, the detection generated by the self-check operation does not report a vehicle detection to the remainder of the system.

[0058] The detector may incorporate a “sequential scan” mode, in which each of the inductive loops monitored by the module is activated and monitored individually. The detectors may be “scanned” in sequential order, so that no two detectors are active simultaneously. The sequential scan mode may require a maximum of 25 milliseconds per detector loop, for example. The detector may incorporate a mechanism such that the sequential scan mode may be synchronized across multiple detector modules. Each detector module may provide a serial communications link for the transfer of data and status to the LPS.

[0059] The serial link may conform to the EIA RS-485 for two-wire (half-duplex) interface standards, for example. The serial link may provide electrical isolation from internal grounds and logic voltages. The detector module may include an addressing capability such that multiple modules may be polled as slaves on a single communications link in a multi-drop fashion.

[0060] The loop detector rack may be configured and dimensioned according to EIA Standard RS-310 (19-inch rack), for example. The loop detector rack may be configured and dimensioned to allow the installation of multiple loop detector modules. The loop detector rack may include wiring to the Inductive Loop Interface Termination Panel for all inductive loop lead-in cables.

[0061] The loop detector rack may provide wiring to the EGMS Termination Panel for all vital output signals. This includes “Health” vital outputs and “Detect” vital outputs. The loop detector rack may provide wiring termination points for an external isolated 12 vdc power supply (or non-isolated 12 vdc source if isolation is performed within the detector rack equipment). The rack may distribute the power from the power supply as necessary to energize all installed loop detector cards.

[0062] The loop detector cards may be incorporated into the Logic Processing System Rack if desired. The Logic Processing System (LPS) may be configured and dimensioned according to EIA Standard RS-310 (19-inch rack), for example. The LPS may meet or exceed the environmental requirements as specified in section 11.5.1 of the AREMA Signal Manual (2000) document. These requirements include temperature, humidity, voltage transients, vibration, and shock.

[0063] The LPS may operate from an external nominal 12 vdc power source, for example. The voltage range may be 9 vdc minimum to 18 vdc maximum. The maximum ripple may be 500 millivolts peak to peak, for example. The LPS power supply may be electrically isolated from the 12 vdc power source. This may be achieved using either internal power isolation or the use of an external 12 vdc isolated supply.

[0064] The LPS may include all microprocessor, logic, and interface circuitry as required for functional operation as specified in this section. The LPS may include all firmware, software, and database programming as required for functional operation as specified in this section. All firmware and software residing in the LPS may be programmed and installed by the manufacturer of the LPS. Firmware or software may be protected from modifications by the equipment user. All initial database items may be configured by the manufacturer of the LPS. However, database changes may be made according to site-specific needs. The LPS may provide vital 12 vdc input circuits, to allow an interface to the vital loop detector “Health” confirmations. A nominal 12 vdc signal at each of these inputs, for example, may indicate that the corresponding detector is functioning properly. A lack of signal at each of these inputs may indicate that the corresponding detector is malfunctioning.

[0065] The LPS may provide 16 vital 12 vdc input circuits, to allow an interface to the vital loop detector “Detect” confirmations. A nominal 12 vdc signal at each of these inputs may indicate that the corresponding detector does not detect the presence of a vehicle within its detection zone. A lack of signal at each of these inputs may indicate that the corresponding detector detects the presence of a vehicle within its detection zone. The LPS may provide vital 12 vdc input circuits, for the monitoring of the “Gate Horizontal” switches for each of the entrance and exit gates within the Crossing System.

[0066] A nominal 12 vdc signal at each of these inputs may indicate that the corresponding gate is in the fully horizontal position. A lack of signal at each of these inputs may indicate that the corresponding gate is in a partial-to-full vertical position. The LPS may provide vital 12 vdc input circuits, for the monitoring of the “Gate Vertical” switches for each of the entrance and exit gates within the Crossing System. A nominal 12 vdc signal at each of these inputs may indicate that the corresponding gate is in the fully vertical position. A lack of signal at each of these inputs may indicate that the corresponding gate is in a partial-to-full horizontal position. The LPS may provide one vital 12 vdc input circuit, for the monitoring of the Grade Crossing Warning System Crossing Relay (XR) signal. A nominal 12 vdc signal at this input may indicate that the warning system is not activated. A lack of signal may indicate that the warning system is active and a train is approaching.

[0067] The LPS may provide two vital 12 vdc input circuits, for the monitoring of Grade Crossing Warning System Island Circuit (ISLAND) signals. A nominal 12 vdc signal at both of these input may indicate that no train is occupying the crossing. A lack of signal on either of these inputs may indicate that the crossing island circuit is occupied by a train. The LPS may provide vital outputs as a “EGMS Health” confirmation. This output may signal the Grade Crossing Warning System and the PTC System of any failures/faults related to the EGCS that result in the loss of exit gate functionality. The EGMS Health output may remain active if the EGMS enters backup Timed EGOM due to detector failure. This output may generate an isolated, vital 12 vdc voltage at such time as the LPS, and corresponding components are functioning properly. This output may not generate a voltage when any failure of the LPS circuitry, wiring, or power supply are present.

[0068] The LPS may provide one vital output as a “Detector Health” confirmation. This output may signal the Grade Crossing Warning System and the PTC System of any failures/faults related to the detectors. It does not necessarily reflect the health status of the LPS. The EGMS may be in Timed EGOM and exit gates may be functional, regardless of the Detector Health output state. This output may generate an isolated, vital 12 vdc voltage, for example, at such time as the detectors and corresponding components are functioning properly.

[0069] The LPS may provide one vital output as a “Detect” confirmation. This output may signal the PTC System of any encroaching vehicular traffic and the need to degrade the PTC signal to the train. This output may generate an isolated, vital 12 vdc voltage at such time as the LPS indicates that all loop detectors are functioning properly and that no loop detectors are detecting vehicular presence. This output may generate an isolated, vital 12 vdc voltage at such time as the LPS indicates that all loop detectors are functioning properly and one or more ISLAND input circuits is inactive (“train occupying island”), regardless of vehicle presence detection. This state may prevent false vehicle detection and possible PTC signal degradation caused by the train itself as it passes the loop detectors. This output may generate an isolated, vital 12 vdc voltage at such times as the LPS indicates that all loop detectors are functioning properly and the XR input circuit is active (“no trains approaching the crossing”). This state may prevent PTC signal degradation when no train is approaching the crossing and the warning system is not active. When XR is active, vehicular traffic through the MTCD is normal and expected. This output may not generate a voltage when any loop detector health output is inactive, or when any loop detector indicates vehicle detection, subject to the state of the XR and ISLAND input circuit.

[0070] The LPS may provide vital outputs to control the exit gates. Each output may generate an isolated, vital 12 vdc voltage at such time as the LPS determines that the corresponding exit gate(s) may be in the horizontal position. Each output may not generate a voltage at such time as the LPS determines that the corresponding exit gate(s) may be in the vertical position.

[0071] The LPS may provide vital outputs to allow override control of the entrance gates. The output may generate an isolated, 12 vdc voltage, for example, at such time as the LPS determines that it is safe to allow the entrance gates to move to the vertical position. The output may not generate a voltage at such time as the LPS determines that the entrance gates must move to or remain in the horizontal position. If the output is active (12 vdc present), the crossing warning system may maintain normal control of the entrance gates. The LPS may force the exit gates to the horizontal position, but may not be able to raise the entrance gates to the vertical position independent of the crossing warning system.

[0072] The LPS may provide a serial communications link for the transfer of data and status from each VLD module. The serial link may conform to the EIA RS-485 for two-wire (half-duplex) interface standards, for example. The serial link may provide electrical isolation from internal grounds and logic voltages. The serial link may have the capability to communicate with multiple VLD modules as the master on a single communications link in a multi-drop fashion.

[0073] The Logic Processing System Rack (LPS rack) may be configured and dimensioned according to EIA Standard RS-310 (19-inch rack), for example. The LPS rack may be configured and dimensioned to allow the installation of all electronics and circuitry required for the proper operation of the LPS. The LPS rack may provide wiring to the EGMS Termination Panel for the XR and ISLAND vital inputs. The LPS rack may provide wiring to the EGMS Termination Panel for gate horizontal position vital inputs. The LPS rack may provide wiring to the EGMS Termination Panel for gate vertical position vital inputs. The LPS rack may provide wiring to the Detector Output Termination Panel for loop detector vital input signals. This may include “Health” vital inputs and “Detect” vital inputs.

[0074] The LPS rack may provide wiring to the EGMS Termination Panel for Exit Gate Control vital outputs. The LPS rack may provide wiring to the EGMS Termination Panel for Entrance Gate Hold vital outputs. The LPS rack may provide wiring to the EGMS Termination Panel for “EGMS Health” vital outputs. The LPS rack may provide wiring to the EGMS Termination Panel for “Detector Health” vital outputs. The LPS rack may provide wiring to the EGMS Termination Panel for “Vehicle Detection” vital outputs. The LPS rack may provide wiring termination points for an external 12 vdc power source, for example. The rack may distribute the power from the power supply as necessary to energize all LPS electronics and circuitry.

[0075] One or more isolated 12 vdc power supplies may be provided as an integral part of the EGMS. The power supply may accept an input voltage nominally 12 vdc, for example. The power supply may provide the necessary output voltages, of sufficient current to provide operational power to all EGMS equipment, including all loop detectors, the LPS, and the Maintenance Diagnostics Display Panel. The power supply may provide electrical isolation between the 12 vdc input voltage and the 12 vdc output voltage, for example. The power supply may be an integral part of the LPS rack, a plug in module within the LPS rack, or configured and dimensioned according to EIA Standard RS-310 (19-inch rack), for example.

[0076] The EGMS Maintenance Diagnostic Display Panel (MDDP) may provide an interactive means by which the user/operator may observe current and past system operation. The MDDP may include a software-controlled changeable alphanumeric display capable of presenting system information to the user. The MDDP display may be visible and legible from a distance of three (3) feet in all typical ambient lighting situations (e.g. bright sunlight, night, etc), for example. The display may include a backlight or other mechanism to make the display visible and legible in low ambient light conditions.

[0077] The MDDP may include a keypad or other means by which the user may interactively select the desired information to be displayed. The MDDP may retrieve information from the LPS for display to the user. All information may be obtained through the LPS, rather than through additional external mechanisms. The MDDP may present the information in a concise, user-friendly manner. Use of menus and full-text options may be included.

[0078] The MDDP may present the following information: Current time and date, as known by the LPS; Current operational mode and state of the LPS; Current states of all vital inputs, as determined by the LPS; Current states of all vital outputs, as determined by the LPS; and Time, date, type, and related information concerning all events in the LPS event log.

[0079] The MDDP may include a bidirectional serial data port properly configured and programmed to allow access to all MDDP data via a remote device such as a laptop computer. Any public-domain communications protocol utilized by the MDDP may be referenced and the corresponding standards adhered to. Any proprietary communications protocol utilized by the MDDP may be made available in printed and electronic format with the system.

[0080] The inductive loop detectors may be terminated for the loop lead-in wiring. The Inductive Loop Termination Panel (ILTP) may provide a wiring location for all such field termination. The ILTP may be configured and dimensioned according to EIA Standard RS-310 (19-inch rack), for example. The ILTP may be configured and dimensioned to allow proper, neat and orderly field termination of all inductive loop lead-in cabling. All termination points on the ILTP may be labeled clearly as to function. Loop Interface Termination may be achieved using AAR-Standard terminal posts for all field wiring. Loop Interface terminals may be provided for the termination of up to sixteen (16) primary inductive loops. Loop Interface terminals may be provided for the termination of up to sixteen (16) self-check inductive loops.

[0081] Signals between the Inductive Loop Detector Rack and the Logic Processing System Rack may be wired through the EGMS Termination Panel (ETP). By providing a single location for interconnected signals between the Loop Detector Rack and the LPS Rack, testing and monitoring of pertinent signals is simplified. The ETP may be configured and dimensioned according to EIA Standard RS-310 (19-inch rack). For example: the ETP may be configured and dimensioned to allow proper, neat and orderly interconnect wiring of all signals between the Loop Detector Rack and the LPS Rack. The ETP and REIP terminations may be combined within a single panel. All termination points on the ETP may be labeled clearly as to function. All ETP wiring connections may be achieved using WAGO “cage clamp” terminals. ETP terminals may be provided for the following signals between the Loop Detector Rack and the LPS Rack: “Detect” vital signals and “Detector Health” vital signals.

[0082] Signals between the EGMS and the balance of the railroad equipment within the house may also wired through the ETP. By providing a single location for the wiring of signals between the EGMS and the remainder of the railroad equipment, testing and monitoring of pertinent signals may be simplified. For example:

[0083] One railroad grade crossing predictor “XR” vital input;

[0084] Two railroad grade crossing predictor “ISLAND” vital inputs;

[0085] Eight (8) gate horizontal position vital inputs;

[0086] Eight (8) gate vertical position vital inputs;

[0087] Two (2) Exit Gate Control vital outputs;

[0088] One (1) Entrance Gate Hold vital output;

[0089] One (1) “EGMS Health” vital output;

[0090] One (1) “Detector Health” vital output; and

[0091] One (1) “Vehicle Detection” vital output.

[0092] The inductive loops may include the wiring that constitutes the loop itself, along with the “lead-in” wiring between the loop and the railroad house. For proper, reliable operation, the loop material and installation specifications may be followed.

[0093] For more information on loop installation, the document “Saw Cut Loop Installations” is available on-line at www.renoae.com. These specifications detail the installation of loops into existing asphalt pavement. In new pavement, the use of “pre-formed” loops may be desired. For example, Inductive loops may be installed in saw cuts in the pavement, per the following:

[0094] Saw slots may be ¼ inches wide, per installation requirements of the loop wire. Saw slots may be the proper depth (1-½ to 3 inches) and clean, with no sharp comers. At corners and right-angle turns, 45-degree angle cuts may be used to lessen the severity of wire bends. The deeper depth should be used in softer pavement materials. Saw slots may be a minimum of 12 inches from any pavement edge, and may be a minimum of 6 inches from any crumbling, damaged, or severely cracked pavement. Saw slots may not cross any boundary between pavement material types, nor may the saw slots be made in any material subject to movement, shifting, or other action that may cause abrasion or breakage of the loop wire, without acceptable safeguards to protect against loop wire damage. Prior to installation of loop wire, all debris from saw slots may be remove using compressed air. Prior to installation of loop wire, saw slots may be examined to ensure that the bottom and sides of the slot are smooth and contain no sharp projections. Inductive loop wire may be of proper type for use as an inductive loop. Loop wire may be single-conductor, #16 stranded copper wire with dual-jacketed insulation designed to allow movement of the inner jacket within the outer jacket, for example. Loop wire insulation may be rated for direct burial.

[0095] Loop wire insulation may be cross linked polyethylene (XLPE) or polyester. Polyvinyl Choride (PVC) insulation (TFFN, THHN, or THHN-THWN) may not be used in loop wires, due to their moisture-absorbing properties. Loop wire may incorporate water displacement gel to prevent the intrusion of moisture into the insulation or between the inner and outer jackets.

[0096] Each loop may consist of a single length of wire, without splices, up to the point where the loop wire is spliced into the lead-in cable. Inductive loop wire may be installed as follows:

[0097] One end of each loop wire may be located at the point where the loop wire is spliced into the lead-in cable. The loop wire may then be installed in the loop saw cut, and the other end of each loop wire may terminate where the loop wire is spliced into the lead-in cable. As each loop wire is installed, it may be pressed to the bottom of the saw cut using a wooden stick or roller to ensure that the wire is seated flat on the bottom of the cut or flat on top of the previous wire turn. No sharp objects should be used for this operation.

[0098] The primary detection loop may be installed in the saw cuts first. The number of turns of wire within the loop is determined by the loop perimeter using the following table: TABLE 1 Loop Perimeter Number of turns 10 feet-13 feet 4 14 feet-26 feet 3 27 feet-80 feet 2 81 feet and up 1

[0099] The self-check loop may be installed in the saw cut last. The self-check loop may consist of a single turn of wire. A “backer rod” or other means may be used within the loop saw slots on top of the loop wires, to keep the loop wires pressed to the bottom of the saw slot during the application of the loop sealant. After all loop wires are installed in the saw slots, an approved loop sealant may be applied according to manufacturer's instructions. The sealant may be selected to match the application and the pavement type.

[0100] Loop lead-in cable (the wire leading from the loop to the railroad bungalow and the EGMS equipment) may be installed as follows:

[0101] The loop wire may be spliced into the loop lead-in cable at a pull-box, hand-hole, or cabinet located near the loop installation. The loop lead-in cable may be 9-conductor cable designed for direct burial without the need for conduits or other protective devices. The loop lead-in cable may be continuous (no splices) from the railroad bungalow to the loop wire splice. Each splice from the loop wire to the loop lead-in cable may be soldered, even when a crimp splice is used. Each splice from the loop wire to the loop lead-in cable may be protected with a moisture-proof seal. Each detector loop set, consisting of a primary detection loop and a self-check loop, requires four wire conductors to the railroad bungalow. Thus, one 9-conductor cable may be used as a loop lead-in cable for two detector loop sets. Loop lead-in cables may be terminated in the railroad bungalow at the Inductive Loop Termination Panel.

[0102] The following sections describe specifications relating to the EGMS software functionality. The standard operating mode of the EGCS may be “dynamic exit gate mode”, which monitors the detection of vehicles within the crossing area to govern the decent of the exit gates. This is the normal mode of operation when all detectors are functioning properly.

[0103] The LPS may perform logic processing as necessary to provide safe, reliable control of the crossing's exit gates based on the monitoring of the crossing XR/ISLAND signals, the gate position inputs, and the loop detector inputs.

[0104] If the XR signal is applied (12 vdc), the LPS may de-energize the Exit Gate outputs so that the exit gates move to/remain in their vertical positions.

[0105] If one or more of the entrance gates are in the fully vertical position (as indicated by the Gate Vertical vital inputs), the LPS may de-energize the Exit Gate outputs so that the exit gates move to/remain in their vertical positions.

[0106] Upon de-energization of the XR signal (and subsequent dropping of the entrance gates), the LPS may initiate a “maximum gate descent time” counter, which may continue until all entrance gates reach the horizontal position. If any entrance gates fail to reach the horizontal position within the maximum allowable time, the LPS may raise all exit gates and enter a failure mode until reset by the user.

[0107] Upon de-energization of the XR signal (and subsequent dropping of the entrance gates), the LPS may enter the “EGCT Delay” mode, in which the LPS times the user-programmable Dynamic Exit Gate Clearance Time delay. During the timing of EGCT Delay, the exit gates may remain in the vertical position regardless of loop detector inputs. Note that the user may program the EGCT Delay to a value of zero (0) seconds, in which case the LPS may enter the “Gate Drop” state immediately upon de-energization (and subsequent dropping of the entrance gates) of the XR signal.

[0108] Upon completion of the EGCT Delay, the LPS may enter the “Gate Drop” mode, in which the LPS monitors the loop detector inputs and energizes the Exit Gate outputs when no vehicular traffic is detected within the crossing area.

[0109] The detectors' effects on Exit Gate control may be governed by the current states of the entrance and exit gates for each direction of travel: If no entrance gates or exit gates are in the fully horizontal position, a vehicle detection upon the detectors within a particular travel direction may cause the Exit Gate output for that travel direction to de-energize, thus raising that exit gate.

[0110] If an entrance gate is in the fully horizontal position for a particular travel direction, the detector immediately adjacent to that entrance gate and detecting vehicular traffic in that direction, may be inhibited from detection. This is to prevent vehicles from “nosing” under a gate to activate a detector and thus raise an exit gate arbitrarily. Based on a user-programmable entry, this option may be negated and the entrance gate detector may continue to monitor vehicular traffic.

[0111] If an entrance gate is in the fully horizontal position for a particular travel direction, a detection of vehicular traffic on the detector corresponding to the exit gate of the opposite travel direction may cause the Exit Gate outputs for both exit gates to be de-energized, thus raising both exit gates. This is to prevent vehicle entrapment in cases in which a vehicle drives around a fully horizontal entrance gate.

[0112] The LPS may provide two modes of detector disable, for example, based on user-programmable options:

[0113] Option 1: Disable detectors when all gates horizontal: If the XR signal is de-energized and all Gate Horizontal inputs indicate that the gates are in the full horizontal position, the LPS may inhibit detector-based exit gate control, and may hold the Exit Gate outputs energized until the XR signal is re-energized.

[0114] Option 2: Continue detector monitoring when all gates horizontal: The LPS may continue to monitor all detectors (except for detectors adjacent to entrance gates) regardless of exit gate position, until the Island signal is de-energized. At any time prior to Island de-energization, a vehicle detection may result in the raising of the appropriate exit gate(s).

[0115] The LPS may not inhibit the generation of the “Detect” confirmation output, based on the health and detect states of the loop detectors, regardless of Gate Horizontal inputs. This output is intended to provide an indication of vehicles within the crossing area, independent of gate position.

[0116] If the ISLAND signal is de-energized, the LPS may inhibit the monitoring of loop detectors, and may hold the Exit Gate outputs energized until the XR signal is re-energized. The “Detect” confirmation output may be energized, thus preventing “detection” of the passing train. If the XR signal is energized (indicating no train approaching), the LPS may energize the “Detect” confirmation output, regardless of vehicle detections, thus preventing continuous and/or repeated detection signals to the PTC equipment at times when the crossing is open to vehicular traffic.

[0117] The backup operating mode of the EGMS may be “timed exit gate mode”, and may perform exit gate operation without the use of the vehicle detectors. This may be the mode of operation if one or more of the detectors enter failure mode, or when manually selected by the user.

[0118] The LPS may perform logic processing as necessary to provide safe, reliable control of the crossing's exit gates based on the monitoring of the crossing XR/ISLAND signals and the gate position inputs. At any time the XR signal is applied (12 vdc), the LPS may de-energize the Exit Gate outputs so that the exit gates move to/remain in their vertical positions.

[0119] Upon de-energization of the XR signal (and subsequent dropping of the entrance gates), the LPS may initiate a “maximum gate descent time” counter, which may continue until all entrance gates reach the horizontal position. If any entrance gates fail to reach the horizontal position within the maximum allowable time, the LPS may raise all exit gates and enter a failure mode until reset by the user. Upon de-energization of the XR signal, the LPS may enter the “Timed Gate Drop” mode, in which the LPS initiates a user-programmable “Exit Gate Clearance Time” and a user programmable entrance gate max decent timer. Upon completion of the “Exit Gate Timer”, the LPS may energize the Exit Gate outputs to cause the exit gates to move to the horizontal position.

[0120] Normal control of the entrance gates may be maintained by the Grade Crossing Warning System. However, there are times when the EGMS may determine that the entrance gates should be moved to the horizontal position regardless of the Crossing System state. For example, if an exit gate is held in the horizontal position by some external force or device, the entrance gates should remain down to prevent a vehicle from stopping in the minimum clearance distance. The Entrance Gate Hold output may be wired to an XLC input in such a way that when de-energized, the XLC will activate the warning system lights and drop the entrance gates, and when energized, the XLC will function in the normal manner based on the Warning System operation. The LPS may energize the Entrance Gate Hold vital output if the LPS is fully functional and the exit gates are determined to be operating properly. The LPS may de-energize the Entrance Gate Hold vital output based on a user-programmable mode of operation, for example:

[0121] Hold Entrance Gates until Exit Gates Vertical: If so programmed, the Entrance Gate Hold output may remain de-energized at any time the exit gates are not all in the fully vertical position. This mode keeps the entrance gates down until the exit gates ascend fully.

[0122] Hold Entrance Gates when Exit Gates Horizontal: If so programmed, the Entrance Gate Hold output may remain de-energized at any time any exit gate is in the fully horizontal position. This mode allows the entrance gates to raise as soon as the exit gates begin their ascent. The entrance gates would be held down only if the exit gates fail to begin rising.

[0123] The LPS includes a serial communications link to all Vital Loop Detector modules to monitor detector data and status. This link operates independently of the discrete vital “Health” and “Detect” inputs from the detector modules.

[0124] The VLD Communications Link may permit the LPS to communicate with each VLD module at least once per second. The VLD Communications Link may permit the LPS to retrieve, store, update, and display any configuration data maintained within the VLD modules. This data includes, but is not limited to, detector sensitivity, sequential scan mode selection, and vital check loop activation interval time.

[0125] The VLD Communications Link may permit the LPS to retrieve, display, and log status information provided by the VLD modules. This data includes, but is not limited to, current operation frequency for each loop, time since last vital check loop activation for each loop, current vehicle detection and health status for each loop, and detailed results of internal diagnostics and loop monitoring. The VLD Communications Link may remain operable to each VLD module regardless of the vital “Health” output state of the VLD module.

[0126] The LPS maintains a running, non-volatile history of system operation in an EGMS Event Log. This log includes normal operation and abnormal/failure conditions. The log is viewable from the diagnostic display panel and is made available for upload to computer via a serial connection. The LPS may maintain an event log (to include event type and time stamp) within non-volatile memory, into which may be recorded the following events, for example:

[0127] Device Power-up;

[0128] Any internal device failure/fault detection;

[0129] Any user log-in via the MDDP or serial communications link;

[0130] Any user change to device database settings, to include user log-in ID, previous data value, and new data value;

[0131] All state transitions of the XR signal;

[0132] All state transitions of the ISLAND signals;

[0133] All state transitions of the Loop Detector “Detect” inputs, during times in which the XR and/or ISLAND signals are in the de-energized state;

[0134] All state transitions of the Gate Position inputs;

[0135] All state transitions of the Loop Detector “Health” inputs;

[0136] All state transitions of the “EGMS Health” output;

[0137] All state transitions of the “Detector Health” output;

[0138] All state transitions of the LPS “Exit Gate Control” outputs;

[0139] All state transitions of the “Entrance Gate Hold” output; and

[0140] All transitions between Detectorized Exit Gate mode, Timed Exit Gate mode, and/or Disabled Exit Gate mode.

[0141] The LPS may supply events within the event log to the Maintenance Diagnostic Display Panel upon user request. The LPS event log may be of sufficient capacity to maintain 100 typical train crossing movements, and 10000 individual events, for example. The LPS event log may be of a “Ring Buffer” type, such that when the buffer is full, the most recent event may replace the oldest event. The most recent event occurrences may always be accessible.

[0142] Whereas the invention has been shown and described in connection with the preferred embodiment thereof, it will be understood that many modifications, substitutions and additions may be made which are within the intended broad scope of the appended claims. There has therefore been shown and described an improved railroad crossing warning system which accomplishes at least all of the above stated advantages. 

What is claimed is:
 1. A gate system for an intersection of a railroad track and roadway, the roadway having two lanes of opposing vehicular traffic, the opposing vehicular traffic generally having a first direction and a second direction, comprising: a first entrance gate located proximate a first lane of the roadway, the first entrance gate operable between an open and closed position to control vehicular travel across the railroad track from the first direction; a first exit gate located proximate the first lane of the roadway, the first exit gate operable between an open and closed position to control vehicular travel across the railroad track from the second direction; a second entrance gate located proximate a second lane of the roadway, the second entrance gate operable between an open and closed position to control vehicular travel across the railroad track from the second direction; a second exit gate located proximate the second lane of the roadway, the second exit gate operable to control vehicular travel across the railroad track from the first direction; one or more detectors to detect a vehicle proximate to the intersection; one or more crossing relays to detect a train proximate the intersection; and a controller connected to the one or more detectors and the one or more crossing relays to operate the gates.
 2. The gate system of claim 1, wherein the one or more detectors are inductive loops.
 3. The gate system of claim 1, further comprising first and second entrance detectors respectively located proximate the entrances of the first and second lanes, first and second exit detectors respectively located proximate the exits of the first and second lanes.
 4. The gate system of claim 1, wherein the railroad track is two railroad tracks having an island, the island generally defined as the area of the first and second lanes between the two railroad tracks.
 5. The gate system of claim 4, further comprising first and second island detectors respectively located proximate the first and second lanes in the island.
 6. The gate system of claim 1, wherein the controller operates the exit gates to allow a vehicle to exit the intersection when the one or more detectors detect a vehicle.
 7. The gate system of claim 1, wherein the one or more detectors self-check for failure.
 8. The gate system of claim 1, wherein a failure of the exit gates is a failure in the open position.
 9. The gate system of claim 1, wherein a failure of the entrance gates is a failure in the closed position.
 10. The gate system of claim 1, wherein a timer controls the operation of the gates.
 11. A method for controlling gates at an intersection of a railroad track and roadway, comprising the steps of: detecting a train proximate the intersection; monitoring the status of one or more detectors proximate the intersection to determine presence of a vehicle proximate the intersection; and operating one or more exit gates if a vehicle is detected proximate the intersection.
 12. The method of claim 11, further comprising the steps of: monitoring the status of a first and second entrance detector, the first and second entrance detectors respectively proximate a first entrance and a second entrance of the intersection, to determine the presence of a vehicle proximate the entrances; closing the entrance gates if no vehicle is detected at the entrances; and temporarily disabling the entrance detectors.
 13. The method of claim 12, further comprising the steps of: monitoring the status of a first and second exit detector, the first and second exit detectors respectively proximate a first exit and a second exit of the intersection, to determine the presence of a vehicle proximate the exits; and closing the exit gates if no vehicle is detected at the exits.
 14. The method of claim 13, further comprising the steps of: monitoring the status of a first and second island detector, the first and second island detectors respectively proximate a first lane and a second lane of the intersection, generally between the entrances and exits of the intersection, to determine the presence of a vehicle between the entrances and exits of the intersection; and closing the exit gates if no vehicle is detected proximate the island.
 15. The method of claim 14, further comprising the step of temporarily disabling the exit detectors.
 16. The method of claim 14, further comprising the step of temporarily disabling the island detectors.
 17. The method of claim 11, wherein the one or more detectors are inductive loops.
 18. The method of claim 11, wherein the inductive loops self-check for failures.
 19. The method of claim 18, wherein the gates are operated by a timer if a failure is detected.
 20. The method of claim 11, wherein the one or more exit gates are opened upon failure. 